The present invention relates to a procedure for the intravascular catheterization of higher mammals, and in particular to a method and device for imaged retrograde arterial catheterization without radiographic guidance. Specifically, the invention pertains to the use of a catheter-mounted Doppler ultrasound transceiver to selectively guide the cathether along the arterial tree towards the heart, and the use of an ultrasonic imaging transducer to generate an image of the area surrounding the catheter tip or at a point located distally therefrom.
Vascular catheterization is practiced medically for a variety of reasons, and is used in both diagnostic and therapeutic procedures. In the case of radioangiography, for example, the catheter is used to deliver a radiopaque dye to a desired point in the circulatory system. The dye is then injected and is passively distributed while being visualized via fluoroscopy or radiography, providing an indication of blood flow and distribution. Alternatively, the catheter may carry a device for the treatment of intra-vascular defects, such as an inflatable balloon which can be used to enlarge an area of vascular constriction.
Diagnostic devices can be attached to such catheters so as to allow the taking of intravascular measurements. It has been suggested elsewhere to attach an ultrasonic transceiver to a vascular catheter, either at or near its tip. Patents issued to Liston, et al. (U.S. Pat. No. 3,443,433), Millar (U.S. Pat. Nos. 4,175,566, 4,665,925, 4,771,782 and 4,771,788), McLeod, et al. (U.S. Pat. No. 4,237,729), and Johnston (U.S. Pat. Nos. 4,637,401 and 4,674,336) reveal the use of ultrasonic transceivers in conjunction with arterial or venous catheters. In all of these references, however, the ultrasonic element is introduced to measure blood flow velocity only.
Moreover, these references teach only conventional methods of positioning a catheter. The placement of a catheter into or near the left heart has, until now, been accomplished by fluoroscopically monitoring the catheter's progress through the circulatory system. The reference of Johnston (U.S. Pat. No. 4,637,401) proposes inserting the catheter in a vein and allowing it to be pulled downstream to the site of interest; this technique is unsuitable, however, for reaching the left heart chambers and the blood vessels immediately downstream.
Catheterization of the left heart requires upstream or retrograde insertion of a catheter and has typically involved the use of fluoroscopic equipment, which is unavoidably bulky and expensive and therefore restricts the available locations in which catheterizations can be performed. A further drawback of fluoroscopy-guided catheterization arises when the catheter is insufficiently radiopaque, requiring the use of radiopaque indicators or plugs inserted at the catheter tip, as suggested in U.S. Pat. No. 4,577,637. Yet another shortcoming is the undesirable exposure of the patient to radiation over long time periods, which necessarily occurs during fluoroscopy and which may pose a health risk as in the case of a pregnant patient. Still another drawback is the inability of conventional catheterization systems to accurately locate the specified position of the catheter tip in the heart or other area of the circulatory system, or to provide an image of the immediate area surrounding the catheter tip.